Skeletal and Dental Changes Between Fixed and Removable Maxillary Expanders

Objectives: Determine skeletal and dental changes with fixed and removable maxillary expanders analyzed through CBCTs.
Methods: CBCT images of 66 patients (32 removable maxillary expanders and 34 fixed maxillary expanders) were analyzed using AVIZO®. Each patient had CBCTs taken prior to maxillary expansion (T1), and again when the appliances were removed at 4-6 months (T2). 14 skeletal landmarks and 30 dental landmarks were manually identified. 21 distances were measured between corresponding right and left skeletal and dental landmarks. Ten CBCT images were analyzed 3 times to determine the reliability of the landmarking. Statistical analyses included descriptive statistics, ANOVA and a t-test.
Results: The reliability for the landmarking procedure was successful (ICC >0.973). The fixed maxillary expander resulted in an increase in all 21 distances, with the greatest increase being between the 16 and 26 mesial buccal pulp horn (4.67mm). The removable expander resulted in an increase in only 17 distances, with a decrease in 13 to 23 root apices (-0.94mm), 13 to 23 buccal alveolar bone (-1.23mm), 14 to 24 root apices (-1.16mm), and 14 to 24 buccal alveolar bone distances (-1.16mm). The fixed expander group had greater expansion compared to the removable expander in all distances except for 11 to 21 pulp horns, and 13 to 23 pulp horns.
Conclusions: The distances between pulp horns of the canines, first premolar and molars increased more than the distances of the root apices and adjacent buccal alveolar bone for both appliances suggesting that both appliances caused some tipping of the teeth. However, the fixed appliance group had expansion of all dental landmarks measured suggesting more lateral movement of the teeth. Overall, the fixed appliance provided greater expansion of the palate compared with the removable appliance.